1. Field of the Invention
The present invention relates to reciprocating cutter type trimmers and more particularly to a reciprocating cutter trimmer in which a pair of upper and lower blades are subjected to reciprocation by means of power transmission means such as eccentric cams.
2. Description of the Prior Art
In the reciprocating cutter type trimmer used for trimming work of trees and grass, such as clipping of weeds at ridges and service waterways, mowing of turfs and trimming of hedges, the output of a power source such as an internal combution engine arranged at one end of an operation rod is typically transmitted to a blade unit through a power transmission unit to reciprocate a pair of upper and lower elongated blades in the longitudinal direction so as to cut trees and grass.
When reciprocating cutter blades are reciprocated to do work in this manner, the edge of the blade will be worn out or broken. Then, for exchanging of the blade or polishing thereof, the power transmission unit must be disassembled and troublesome removal, dismounting and assembly work has to be done. Under the circumstances, in order to facilitate such work as the removal and exchange of the blade, it has hitherto been known to make only the blade unit separate as described in, for example, Japanese Utility Model Application Laid-open No. Hei 4-60018 and Japanese Utility Model Application Laid-open No. Hei 2-6422 as well as the specification of Japanese Utility Model Application No. Hei 3-106427. FIG. 5 is a plan view showing the essential part of such a conventional separation type blade.
In FIG. 5, a crank lever 60 for conversion of rotary motion into linear reciprocation is formed with a laterally elongated hole 61 in which a cam, not shown, is received at one end thereof, whereby as the cam rotates within the elongated hole 61, rotary motion of the cam is converted into linear reciprocation of the crank lever 60. A connecting lug 62 is formed at the other end of the crank lever 60 and it is removably fitted in a cut 71 formed at one end of a blade 70. With the lug fitted in the cut in this manner, the crank lever and the blade are made to be integral with each other for linear reciprocation.
In the above-described conventional reciprocating cutter type trimmer, however, when the trimmer is used frequently in, for example, work which uses only the tip of the blade, for example, such work as clipping of grass at ridges, only the tip (fore end) of the blade is often worn out or broken, raising a problem that the blade must be exchanged or ground frequently for a small frequency of operation.